Various types of calipers are known for measuring different objects. A caliper must be properly applied against the object to take the desired measurement, and when measuring the thickness of between two sides of an object, a caliper must be held at right angles to the piece.
In the field of orthopedics, calipers are used for measuring a knee and a leg for a knee brace. As illustrated in FIG. 1, an exemplary method for measuring a knee includes using a marker to apply landmarks on the patient's leg such as at the medial joint space, and along the tibial crest at the tibial tuberosity and a distance below which is depicted in FIGS. 1A and 1B. Referring to FIG. 1C, a conventional caliper 102 comes into use in the method by taking the M-L (medial-lateral) measurement 109 at the joint space against the patient's condyles. The caliper 102 includes jaws 104, 106 snugly adjusted against the patient's skin to obtain the measurement and are left in place as the measurement is recorded along the scale 108.
In using the mid patella as a reference point, as depicted in FIG. 1D, above and below circumference measurements 105, 107 are taken at specified distances, and a caliper may also obtain M-L measurements at these locations as well. Next, with the patient standing in a weight bearing position facing a camera, the height of the camera is adjusted at a mid-patella level, and the camera is positioned so it is approximately a specified distance away from the patient. The image captures the leg a specified distance above and below mid patella and is taken of the anterior side of the knee, and an additional image is taken of the lateral side of the knee, as shown in FIGS. 1E and 1F.
The conventional caliper may obtain the M-L measurement and other devices have jaws that slide relative to one another and are indexed to a scale located along a shaft. The clinician must adjust one of the jaws relative to the other jaw, manually move the jaw to press against the patient's soft tissue, and manually removes the jaws from the soft tissue upon completion of the measurement. The force against the soft tissue may exceed comfort levels or may be inconsistently applied from patient to patient.
The conventional caliper 102 may have narrow jaws 104, 106 which may shift over the soft tissue due to their narrow width and may cause discomfort because of sharp tips of the jaws. The jaws are typically elongated and straight, and provide little or any space between areas of the soft tissue within the jaws for adjustment by a clinician. A patient's condyles may have an irregular shape and the narrow jaws may fail to provide an accurate measurement of M/L due to condyle irregularity. In variations, conventional calipers may use contoured “cup-shaped” contact point which extend over the condyles but limit the clinician for placement over the condyles.
Due to a variety of leg shapes, sizes and soft tissue amount, conventional calipers provide inconsistent compression over patients' soft tissue due in part to human error by clinician. The inconsistent compression results in improper measurements for the eventual knee brace and may lead to inferior customization of the knee brace.